If a heroic character was going to get killed off, to me the most likely would be Terra since he's already the tragic hero, and sacrificing his heart within MX in order to destroy MX once and for all is something that I could see happening, though it's probably doubtful.
its also possible that maybe Eraqus destroys himself along with MX so that he can save his children(TAV) and also redeem himself for nearly killing Ven and being willing to kill Terra.
its also possible that maybe Eraqus destroys himself along with MX so that he can save his children(TAV) and also redeem himself for nearly killing Ven and being willing to kill Terra.